Stress Simulation Analysis Of Core-shell Structure Cu@Sn@Ag Soldering Lug Welding Process For Electronic Packaging

Higher power density,smaller size,and higher integration are the development trends of power electronic devices.The third generation of power semiconductor chips widely uses silicon carbide and gallium nitride chips,and it is an important scientific research direction to study chip interconnection materials and technologies that meet the packaging conditions of high power density power electronic modules.Cu@Sn@Ag(Ag coated Sn coated Cu)preset has the advantage of low temperature welding can be used at high temperature,and the cost is relatively low,is the most potential welding material in the future power chip interconnection materials.Based on Cu@Sn@Ag the results of the Cu@Sn@Ag powder thermothermal performance test,this paper simulates the numerical simulation of the joint joint,simulates the influence of welding process parameters and structural parameters of the welding layer on the stress distribution of the welding process,and expects to provide data reference for the application of Cu@Sn@Ag presets,and the main research conclusions of this paper are as follows:1)Thermo-mechanical simulation results of Cu@Sn@Ag solder at different welding temperatures and welding times show that when the welding temperature is240°C ～ 260°C,with the increase of welding temperature,the peak stress of the welding layer after welding gradually decreases,and when the welding temperature is at260 °C ～ 280 °C,it increases slightly,and the stress is the smallest at 260°C,which is3.5 MPa;the welding holding time is within 30 min～120 min,with the extension of the welding insulation time,the stress change of the welding layer is small.The stress at the weld layer above 120 min begins to increase significantly;Comprehensively considering the service performance requirements of the device,when the Cu@Sn@Ag solder lug is used for reflow soldering Si C chip and DBC board,the soldering temperature should be 260°C,and the welding holding time should be controlled at 60 min.2)The thermo-mechanical simulation results under welding holding pressure show that when the welding holding pressure is 1MPa～5MPa,with the increase of holding pressure,the stress at the welding layer also gradually increases,from 1.76 MPa to 21.9 MPa,which is mainly because the greater the pressure applied by welding,the greater the deformation of welding,thereby increasing the welding stress after transient liquid phase diffusion welding of the weld layer,and the welding holding pressure is about 1 MPa.3)Based on COMSOL Multiphysics software,different Cu@Sn@Ag preset layer thickness and cavity presence position on the stress distribution,The results show that: when the thickness of the welding layer is 150 μm,the overall welding stress is the smallest,and the maximum stress value is 1.7 MPa,which is the best layer thickness value.The stress near the cavity is greater than the stress at the edge,and the stress value at the center is the largest,with a maximum stress value of 2.47 MPa.4)The influence of different Cu@Sn@Ag preset cavity diameter,void rate,and randomly distributed cavity existence form on stress distribution shows that with the increase of cavity size,the stress first shows a downward and then rising trend,when the stress is the smallest at 60 μm size,the maximum stress value on the welded layer is 11 MPa.When the void rate of randomly distributed voids increases from 1% to4%,the maximum stress on the solder tab layer increases from 15.3 MPa to 37.6 MPa,an increase of 22 MPa.When there are spherical,ellipsoidal and cylindrical voids randomly distributed in the solder lug layer,the existence of spherical voids has the least stress on the welding layer,the ellipsoid is centered,the cylinder is the largest,and the stress values are 12.4 MPa,60.1 MPa,and 217 MPa,respectively.